1. Field of the Invention
The present invention relates to a reciprocating compressor, and more particularly, to a structure for fixing a motor stator of a reciprocating compressor capable of simplifying a structure for supporting a motor stator and capable of reducing a fabrication cost by facilitating a fabrication.
2. Description of the Conventional Art
Generally, a reciprocating compressor is an apparatus for compressing a refrigerant as a piston is linearly-reciprocated in a cylinder. The reciprocating compressor is largely divided into two types according to a driving mechanism. One is a type that a rotary motion of a motor is converted into a linear-reciprocation to be transmitted to a piston, and the other is a type that a linear-reciprocation of a motor is directly transmitted to a piston.
FIG. 1 is a sectional view showing one example of a reciprocating compressor in accordance with the conventional art.
As shown, the reciprocating compressor comprises: a casing 100 containing lubricating oil of a certain amount at a bottom thereof; a frame unit 200 elastically supported in the casing 100; a reciprocating motor 300 mounted at the frame unit 200 and generating a linear-reciprocation driving force in an up-down direction; a compression unit 400 for compressing gas by receiving a driving force of the reciprocating motor 300; a resonance spring unit 500 for inducing a resonant motion by elastically supporting a motion of the reciprocating motor 300; and a supporting spring unit mounted between the casing 100 and the frame unit 200 to be respectively positioned at upper and lower portions of the casing 100, for elastically supporting a vibration assembly including the frame unit 200 at upper and lower sides.
The frame unit 200 includes: a first frame 210 for supporting the compression unit 400; a second frame 220 coupled to the first frame 210 and supporting one side of the reciprocating motor 300; and a third frame 230 coupled to the second frame 220 and supporting another side of the reciprocating motor 300. The first frame 210 is located at a position lower than the second frame 220 and the third frame 230.
The reciprocating motor 300 is provided with a winding coil C therein, and includes: an outer stator 310 fixedly coupled between the second frame 220 and the third frame 230; an inner stator 320 inserted into the outer stator 310 with a certain air gap and fixed to the third frame 230; and a mover 330 inserted into the air gap between the outer stator 310 and the inner stator 320 and connected to the compression unit 400.
The compression unit 400 includes: a cylinder 410 fixed to the first frame 210; a piston 420 slidably inserted into the cylinder 410 and coupled to the mover 330 of the reciprocating motor 300; a suction valve 430 mounted at an end surface of the piston 420, for opening and closing a suction channel F; a discharge valve 440 mounted at a discharge side of the cylinder 410, for opening and closing the cylinder 410; a valve spring 450 for elastically supporting the discharge valve 440; and a discharge cover 460 having the discharge valve 440 and the valve spring 450 therein, for covering the discharge side of the cylinder 410.
The resonance spring unit 500 includes: a spring supporting plate 510 coupled to a connection part between the mover 330 and the piston 420; and a first resonance spring 520 and a second resonance spring 530 respectively positioned at an upper side and a lower sides of the spring supporting plate 510, for elastically supporting the mover 330 and the piston 420.
The supporting spring unit includes: a lower supporting spring 610 fixed between a bottom surface of the casing 100 and a corresponding lower surface of the discharge cover 460; and an upper supporting spring 620 fixed between an upper surface of the casing 100 and a corresponding upper surface of the third frame 230.
An unexplained reference numeral 110 denotes a suction pipe, 120 denotes a discharge pipe, 331 denotes a magnet, and 332 denotes a magnet hole.
An operation of the reciprocating compressor will be explained as follows.
When power is supplied to the reciprocating motor 300, a flux formed between the outer stator 310 and the inner stator 320 interacts with a flux formed by a magnet M provided at the mover 330 and thereby the mover 330 is linearly-reciprocated. As the mover 330 is linearly-reciprocated, the piston 420 connected to the mover 330 is linearly-reciprocated up and down in the cylinder 410. As the piston 420 is linearly-reciprocated in the cylinder 410, a pressure difference is generated at a compression space P of the cylinder. By the pressure difference, a refrigerant is sucked, compressed, and discharged at the time of a preset pressure, and the series of processes are repeated. At this time, the resonance spring unit 500 induce a resonant motion of the mover 330 and the piston 420.
The reciprocating compressor constitutes a refrigerating cycle system with a condenser, an expansion valve, and an evaporator. The refrigerating cycle system is mounted in a refrigerator, an air conditioner, a showcase, etc.
In order to enhance a price competitiveness, a fabrication cost of the reciprocating compressor has to be lowered by simplifying a structure of the reciprocating compressor. Also, an assembly productivity of the reciprocating compressor has to be enhanced by simplifying fabrication processes. A construction of a reciprocating motor and a structure for fixing the reciprocating motor are very complicated thus to be required to be improved.
FIGS. 2 and 3 are respectively a sectional view and a disassembled perspective view of a structure for fixing a motor stator of a reciprocating compressor in accordance with the conventional art.
As shown, the inner stator 320 of the reciprocating motor includes: a stacked body 321 formed as a plurality of thin plates having a certain shape are stacked as a cylindrical shape; and fixing rings 322 coupled to both sides of the stacked body 321 and fixing the stacked body 321. The thin plates are arranged towards a center of the stacked body 321.
The third frame 230 includes: a cylindrical fixing portion 231 having a certain thickness and length; a stepped cylindrical portion 233 extendingly formed with a certain length at one side of the cylindrical fixing portion 231 to form a stepped surface 232; and a flange portion 234 curvedly formed at the stepped cylindrical portion 233. The cylindrical fixing portion 231 is formed to be longer than the stacked body 321 of the inner stator.
As the cylindrical fixing portion 231 of the third frame is penetratingly inserted into the stacked body 321 of the inner stator, the third frame 230 and the inner stator 320 are coupled to each other.
A fixing plate 340 having a disc shape is fixedly coupled to the end of the cylindrical fixing portion 231 of the third frame inserted into the stacked body 321 of the inner stator. The fixing plate 340 is fixedly coupled to the cylindrical fixing portion 231 by welding under a state that the fixing plate 340 is inserted into the cylindrical fixing portion 231.
One side surface of the inner stator 320 is supported at the stepped surface 232 of the third frame and another side surface of the inner stator 320 is supported at the fixing plate 340, thereby fixedly coupling the inner stator 320 to the third frame 230.
One side of the upper supporting spring 620 is fixedly supported at the flange portion of the third frame 234. Also, a certain gap is maintained between an outer circumferential surface of the inner stator 320 and an inner circumferential surface of the outer stator 310 so that the mover 330 can be inserted therebetween.
However, in the conventional structure, since the cylindrical fixing portion 231 of the third frame has to be penetratingly inserted into the inner stator 320, the entire outer circumferential surface of the cylindrical fixing portion 231 has to be precisely processed. However, the processing is difficult and the processing cost is high. If a tolerance between the third frame 230 and the inner stator 320 is generated as the inner stator 320 and the third frame 230 are not precisely processed, an air gap between the inner stator 320 and the outer stator 310 is not constantly maintained. According to this, a contact between the inner stator 320 and the mover 330 or a contact between the outer stator 310 and the mover 330 is caused, and a motor efficiency is lowered.
Also, since the cylindrical fixing portion 231 of the third frame is penetratingly inserted into the inner stator 320 and the fixing plate 340 coupled to the cylindrical fixing portion 231 fixes the inner stator 320, the size of the third frame 230 becomes relatively large. According to this, it is difficult to process the third frame 230. Also, since the third frame 230 requires much material and the additional fixing plate 340 is used, a fabrication cost is increased at the time of a massive production.